BACKGROUND: Exercise-induced bronchoconstriction (EIB) following strenuous physical exertion afflicts many people. It can be the cause of sub-optimal performance, symptoms such as cough, dyspnea, wheeze and chest tightness, and can lead people to avoid physical activity. Management of EIB focuses on prevention through pharmaco-therapy and alternate strategies. Single use, pre-exercise, beta-agonists and non-steroidal antiinflammatory agents are recommended.OBJECTIVES: Bronchodilator medications have been commonly used to prevent narrowing of airways after exercise, but anti-inflammatory drugs such as nedocromil sodium have also been used. The objective of this review was to assess the effects of a single dose of nedocromil sodium to prevent exercise-induced bronchoconstriction.SEARCH STRATEGY: We searched the Cochrane Airways Group trials register, the Cochrane Controlled Trials Register, Current Contents, review articles, textbooks and reference lists of articles. We also contacted the drug manufacturer and primary authors for additional citations.SELECTION CRITERIA: Randomised trials comparing a single dose of nedocromil sodium with placebo to prevent exercise-induced bronchoconstriction in patients with EIB over six years of age.DATA COLLECTION AND ANALYSIS: Trial quality assessment and data extraction were conducted independently by two reviewers. Study authors were contacted for confirmation of data.MAIN RESULTS: The combined results from 20 randomised controlled trials involving 280 participants, show that 4 mg, of nedocromil sodium inhaled 15 to 60 minutes prior to exercise significantly reduce the severity and duration of EIB in both adults and children, when compared to placebo. The maximum percentage fall in FEV1 was improved significantly compared to placebo (weighted mean difference 15.5 %; 95% confidence interval:13.2 to 18.1). For the maximum percentage fall in peak expiratory flow rate (PEFR) the improvement was similar: WMD 15.0%, (95% CI 8.3 to 21.6). Nedocromil shortened the time to recover lung normal function from more than 30 minutes with placebo to less than 10 minutes with the drug. It had a greater effect on those patients with more severe exercise-induced bronchoconstriction (defined as an exercise-induced fall in lung function > 30% from baseline). There were no significant adverse effects reported with the short term use of nedocromil. A further search conducted in September 2001 did not yield any further studies.REVIEWER'S CONCLUSIONS: Nedocromil sodium used before exercise reduces the severity and duration of exercise-induced bronchoconstriction. This effect appears to be more pronounced in people with severe exercise-induced bronchoconstriction.